Project Summary Preterm birth is an important risk factor for perinatal mortality and adverse health consequences in childhood and adulthood. In the United States, approximately 10% of all live births were preterm (<37 weeks gestation) in 2012 and it continues to climb. Fresno County, in the San Joaquin Valley of California, is an area of known high air pollution burden and a high prevalence of preterm birth (12%). Wildfires are a significant and increasing source of air pollution in California (CA) that threaten to reverse the progress made over the past decades in air pollution reduction and their effects on pregnant women are not well understood. Furthermore, recent fires are occurring at the wildfire urban interface leading to biomass and structure burning. With increased exposure to wildfire smoke comes increasing concern of health effects of these exposures to inform future regulation. Other biomass burning sources are agricultural waste burning, prescribed burns, and residential wood burning which all can increase air pollution exposure but in more controlled settings and are generally performed during seasons outside the growing fire season. They differ in scope, temperature and chemical composition and may have less severe health effects compared to wildfires. We and other investigators have demonstrated preterm birth risk is sensitive to prenatal exposures to ambient air pollution, including criteria pollutants such as particulate matter and polycyclic aromatic hydrocarbons, a product of incomplete combustion. Moreover, we have found stronger associations in neighborhoods with lower socioeconomic status. This double jeopardy of exposure to pollutants and poverty is hypothesized to contribute to disparities in preterm birth, but sufficient data are often lacking. To address the contribution of wildfire and other biomass burning smoke exposures on preterm birth, and how these relationships may be modified by neighborhood deprivation, we propose to compile a unique group of datasets of fire occurrence, air quality monitoring and modelling, and birth record data for CA (2008-2016) to evaluate the effects of wildfires and intentional burning (agricultural waste, residential wood, and prescribed burns) exposure on preterm birth and to evaluate if the effects differ by the Index of Concentration at the Extreme, a measure of neighborhood deprivation that accounts for extremes based on race/ethnicity and income by census tract. We will compare different models of fire exposure assessment and examine critical periods of pregnancy with regard to preterm birth, while controlling for season. This study will provide estimates of the impact of air pollution exposures from wildfires and other biomass burning on preterm birth. The findings have the potential to inform fire prevention and protection regulation for wildfires, agricultural waste burning, prescribed burns, and residential wood burning.